Just did it. I was using fabric paint on a canvas tote bag and it got smeared bad deep into the texture of the canvas. It was still wet but drying quick so we used toothpicks to scrape off all we could. Then we used Goof Off (after testing a small area) rubbing it in with a stiff little paint brush that we cut short to make a miniature scrub brush. That dissolved the paint but it was still in the fabric. Using a cotton swab we went over it with water. That diluted it further and we were able to use a cloth to blot it out. All this thanks to my husband who held his cool while I was freaking out.
Fabric paint is meant to be permanent on cloth. You really cannot get it out.